Because of the advancements that have been made in the field of medicine, there has been an increase in the transplanting of various organs from a donor to a needy patient. This has certainly been true in the field of opthomology where corneal transplants are almost routinely made. As a part of the surgical procedure involved in a corneal transplant, the donor tissue must be accurately cut into a circular button of a predetermined diameter. The diameter of the donor button will vary depending upon the size of the diseased cornea removed from the patient. At the present time, the donor tissue is cut by a hand-held trephine. If the surgeon does not precisely line up the cutting block holding the donor tissue, or if the trephine is not accurately positioned, the donor tissue may not be accurately cut and may be wasted. There is therefore a need for a device that will ensure a proper, central cut of the donor tissue and which will accommodate the wide range of trephine sizes presently in use. Such a device would not only assure a more accurate and precise cut of the donor tissue, but it would also speed up the surgical procedure. Any such device must of course be easy to use and capable of being sterilized in a autoclave or with gas.